How to Sharpen a Knife Without a Sharpener

If you discover that your knife is not sharp and you don’t have a sharpener with you here are some ways to sharpen your knife on-the-spot to get you through your tight spot until you can sharpen it the right way.

Use the Window of your Car

If you roll down your car window half way and look along the top edge of the window you will discover that this is a good surface to use to sharpen your knife. It is smooth enough and has a slightly rough edge from years of use that can be used to sharpen your knife.

You use the top edge of a car window to sharpen your knife the same way you would use it on a sharpening rod on a serrated knife. Except there is no spinning of the rod. You will find when you do this it feels just like using a sharpening rod. With the window half-way down stroke the blade away from you ‘into the window’ with full long strokes at about a 15-degree angle. Flip the knife blade to the other side and this time run the knife blade toward you this time. Go back and forth to obtain an even edge. Repeat the process until the blade is sharp.

Use the Bottom of a Ceramic Coffee Cup

When you look at a ceramic coffee cup you will see that most of it is polished which would not help you sharpen your knife, but if you flip it over you will find that the underside has an unglazed, unpolished portion where the part of the cup is always rubbing against the table. This is the portion that you sharpen you knife on. By using the same method that you would use to sharpen a knife on a whetstone, you can sharpen your knife there. Just place the ceramic cup upside down on a flat surface and run the full length of your blade along this portion of the cup.

Continue running the blade at the same angle on both sides until the knife feels sharp. This is the most popular method that is used for people that don’t have a sharpener on hand.

Use Glassware

If you can find some glassware with a broken edge or unpolished surface then you can use glassware. Polished surfaces do not do the job well at all. I would say use some sandpaper or emery cloth to knock off the polish of the glass but if you had sandpaper or emery cloth it would be better to use that to sharpen your knife instead!

Unfortunately, finding unpolished glass or broken glass that has a level enough surface is hard to find so you would have to try and break some glass with a level surface obtained which is hard to do and why this method is rarely used.

Like using a ceramic cup you can use glassware in the same way. Although it does not work as well as a ceramic cup you can drag the full length of the blade along the edge of a glass container at about a 20 degree angle to achieve the same results. Just remember that you may not want to use the glass for drinking after this.

A 20 degree angle is good for most knives. If you are sharpening a fillet knife or a boning knife then you would hold the knife at a 15 degree angle and if you have a tactical knife then you would hold it at about a 30 degree angle.

How to Sharpen a Knife with a File

Small Emery File or Nail File

The second most popular item used if you don’t have a sharpener handy is to use a nail file. Just don’t tell your wife you did this! This item can be found in first aid kits or a personal hygiene kit. Place the knife on a hard level surface and use one finger to help hold it in place then follow the same angle and do several passes with the blade away from you on each side until the knife is sharp.

Use Sandpaper

Like an emery file you can use sandpaper to sharpen your knife as well. Depending upon the grit of the sandpaper will help you determine how to sharpen the knife. Coarse grit sandpaper has lower numbers while finer grit sandpaper has higher numbers. You can wrap the sandpaper around a smooth block that you can hold onto to make sharpening the blade easier. Sharpen your knife just like how you would sharpen it with a whetstone by using the same angle and flipping between sides until the blade is sharp.

If you want more details on how to sharpen a knife with sandpaper, read our article, “How to Sharpen a Knife with Sandpaper”.

Use a Brick

This method is not recommended but if you have no other resources at hand this can be a quick way to sharpen a knife until you can do it proper. Again, you would use the same technique of sharpening that you would use by shapening on a whetstone. The bad thing about this method though is that if the brick is not smooth enough it can create large gouges. Again, only use this method as a last result unless you can find a fine-grit brick. Be sure to wash and lubricate the brick before using it to sharpen your knife. After the brick is ready place it on a level surface and use the same techniques as you would use on a whetstone by keeping the same angle, long, full strokes that cover the entire blade, and being sure to flip the knife back and forth to do both sides so you can avoid any unevenness.

Using Concrete to Sharpen your Knife

A better option than using a brick would be to use concrete if you can find a piece of concrete that has a flat surface. Use the same techniques as you would to use a sharpening stone.

Use the Spine of another Knife

Some people may have told you to never use this method to sharpen a knife. In truth, that only applies if it is done the wrong way. By using the spine of the knife (the flat surface along the top back edge of the knife) you can sharpen a knife just fine. The wrong way is to use the blade of one knife to sharpen the other knife. This will only result in an uneven edge that will create gouges and make a bigger mess of things. Now that you know the correct way of doing this you can inform the next person the proper way to do this. Again, do full even strokes on each side of the blade going back and forth at the same angle until the right sharpness is achieved. You do this by holding the knife that you are sharpening upon with the blade down while you move the blade of the knife that needs to be sharpened along the top flat surface of the other knife.

Use the Foot Brace Edge of a Shovel

This is another object to use if you are in a pickle and don’t have any other sources near you. The flat edge of the shovel where you put your foot on to force the shovel into the ground can be used to sharpen the knife. Unlike the brick mentioned above the foot rest of the shovel will be more flat and easier to use to sharpen your knife. Just run the blade across the surface of the shovel for the full length of the blade at about a 20-degree angle several times flipping between each side of the blade every 4 or 5 passes.

How to Sharpen a Knife with a Stone

Using Smooth Flat River Stone

This is probably the source that you can find the easiest when you are outdoors. Using a river stone is mentioned because you can use the water to help lubricate the process for a sharper knife.

Look for the smoothest, flattest stone that you can find and be sure to wash it so that you get rid of any grit that would damage your blade then use the same techniques of sharpening with a whetstone that you would use on your river stone. Keep repeating the process on each side of the blade until you get the knife as sharp as you want it to be. Don’t forget to keep the blade at the same angle so that you won’t create large gouges.

Using a Slate

Using a slate to sharpen the knife is probably the closest thing to a whetstone that you can use. That is because slate is rough enough to do the job but not too rough to create large scratches and gouges on the blade of the knife.

Clean and lubricate the slate with water before starting, then using the same technique as what you would use on sharpening with a whetstone, drag the knife along a slate at about a 20 degree angle several times on each side until the sharpness has been achieved. Remember to go back and forth between each side while you are doing this so that you have an even edge.

How to Strop your Knife on the Fly

Now that your knife is sharpened pretty close to where you want it you can strop it by using these methods on-the-fly if nothing else is available.

Use a Leather Belt

You can use a leather belt to get rid of the burrs and fine-polish the blade in case you have to use a rougher than normal surface to sharpen your blade like a brick or unevenly cut broken glass. The best belts to use are older, used belts. That is because the surface will be rougher and do a quicker job of honing the blade for you. Place the belt on a hard level surface and move the blade away from you in long even strokes at the same angle on both sides of the blade. Just like how you would hone a knife with the proper equipment. Since a leather belt is not the same as a strop you may have to do this for about ten to fifteen minutes before you get the same results.

It has been said that you can use the sear belt of your car in a pinch. But think about it, would you want to degrade the very thing that may save you in an accident later on down the road? I don’t think so, so don’t use seat belts.

Use a Nylon Strap from your Backpack

Instead of using your seat belt maybe the nylon strap from your backpack is available. Just use the same instructions as honing your blade with a leather belt above to achieve the same results. Both of these will remove the burrs from your blade and give you an ultra-sharp edge back on your knife.

Here is a nice video that displays five of the techniques used above for you to view.

This video is from “5 Ways To Sharpen a Knife Without A Sharpener”.